20 years ago I contacted a 2nd hand shop in the very town my Chevelles dealership was originally in,(they were long gone by then)
I talked to a person who owned the shop and gave them my email & phone #.
About 5 years later,I get an email from them saying they got a yardstick in etc. from my cars selling Dealership from a salesman's family,who once worked there.
They gave me their contact info after I bought the items,and contacted that family.
That family contacted me a few years later with some more tidbits..So never give up.